I'm quite in a rush. My betta fish I got yesterday night was soon GOING to be put into a new filtered 5-10 gallon tank. I put in the tap water conditioner and beneficial bacteria inside the water for betta fish. Now, I couldn't put the betta fish in the tank once it got used to the temperature of the water in the cup. The cup is kind of fat, and some tall decorations did make putting the fish into the water. Me and my dad had no net to put in the fish, plus it was getting late so we couldn't drive a 25 minute trip to the pet store especially when the fish is still in the cup.

My idea for putting the betta fish in the tank: Putting the cup in the water, then gently turning it so the betta fish could swim out once it got used to the temperature.

My dad's idea for putting the betta fish in the tank: Dump the water in with the betta fish, without letting the fish get used to the water.

I told my dad NO WAY, to not do it. I guess he didn't care, so since he was in charge, he did it his way. I couldn't do it my way much because the cup couldn't fit into the tank because of tall decorations.
When my dad did this, I cried to myself and argued that the fish could die of this.
A few minutes later I checked the betta fish, only finding it on the side and breathing hard with its gills.

The next day... My betta fish was found sticking to the top decorations. I could tell he wasn't alive because no tiny movements were done, and he wasn't resting either.
I told my dad about this, so he got a spoon and poked the fish. No reaction. Took out the fish. No reaction. So, the fish was dead
I cried once more, then telling my dad that he shouldn't have dumped the fish to the water.

So he blamed me, saying that the water was bad, and the conditioner didn't work, and I didn't set the filter right. I did set the filter right, and I even heard the clicking sound when closing the filter door (I have a square boxed filter). And, I put in the right measurements as well. But my dad saying this... It did make me go unsettled and uneven. I wasn't sure.
My dad said there was no such thing as of dumping a betta fish in the tank, and then he just dies the next day.

Question: Who's right (It doesn't matter who's side you're on, I just need to know the answer so that way that mistake won't happen again) and why.

It does sound as though your fish went into shock because he was not allowed time to acclimate to the new temperature and water.

Sorry for your loss. Your way would have worked fine and probably would have resulted in you still having a fish.

Other possibilities could be poisoning from something leeching into the water (such as something from a decoration), or not enough or too much water conditioner (though this is highly unlikely). However, because of the obvious stress the fish seemed to be in immediately after being put into the tank leads me to believe his cause of death was entirely because he was simply dumped in.

I don't know but, I have done it your dads way before and my fish acclimated just fine. What type of decorations, water conditioner do you have? What is the temperature? Or worse your betta went into shock and died.

It does sound as though your fish went into shock because he was not allowed time to acclimate to the new temperature and water.

Sorry for your loss. Your way would have worked fine and probably would have resulted in you still having a fish.

Other possibilities could be poisoning from something leeching into the water (such as something from a decoration), or not enough or too much water conditioner (though this is highly unlikely). However, because of the obvious stress the fish seemed to be in immediately after being put into the tank leads me to believe his cause of death was entirely because he was simply dumped in.

Because of the time it took for it to happen, I can almost guarantee that it was shock and not these reasons.

I don't know but, I have done it your dads way before and my fish acclimated just fine. What type of decorations, water conditioner do you have? What is the temperature? Or worse your betta went into shock and died.

Well I hope your fish is still okay... I do advise you to use a net or something more gentle. Anyways, my beneficial bacteria is NutraFin Cycle, Biological Aquarium Supplement. My conditioner is NutraFin Aqua Plus, Tap Water Conditioner. My temperature is 77 degrees F. Decorations are tall smooth rocks that form a cave (the decor was like that) and a fake plant.

It does sound as though your fish went into shock because he was not allowed time to acclimate to the new temperature and water.

Sorry for your loss. Your way would have worked fine and probably would have resulted in you still having a fish.

Other possibilities could be poisoning from something leeching into the water (such as something from a decoration), or not enough or too much water conditioner (though this is highly unlikely). However, because of the obvious stress the fish seemed to be in immediately after being put into the tank leads me to believe his cause of death was entirely because he was simply dumped in.

Thank you, I'm not sure about the decoration poisoning because it was more of a smooth rock forming a cave, no glue, and I washed it with hot water.

Well I hope your fish is still okay... I do advise you to use a net or something more gentle. Anyways, my beneficial bacteria is NutraFin Cycle, Biological Aquarium Supplement. My conditioner is NutraFin Aqua Plus, Tap Water Conditioner. My temperature is 77 degrees F. Decorations are tall smooth rocks that form a cave (the decor was like that) and a fake plant.

Yeah I do use a net. I know better to not just dump my fish in. Sorry for your lost.